Treatment of fibrous material



Sept. 14, 1937. T, DUNBAR I 2,093,267

TREATMENT OF FIBROUS MATERIAL Filed NOV. 20, 1934 'N Q h van ATTORNEYPatented Sept. -14, 1937 PATENT, OFFICE TREATMENT F FIBROUS MATERIALThomas L. Dunbar, Watertown, N. Y., assignor to Chemipulp Process,Incorporated, Watertown, N. Y., a corporation of NewYork ApplicationNovember zo, 1934, serial No. 753,894

`Y3 Claims.

This invention relates to the treatment. of iibrous material, and moreparticularly to a normally continuous process of and apparatus for v theproduction of pulp. While the invention is -is of particular value inthe production of so-called semi-chemical pulp from which the lignin isnot entirely dissolved, its applicability is not limited thereto.

v An object of my invention is the provision Aoi! an improved ,processfor the production of pulp, which may be carried on continuously, andthe provision of apparatus suitable therefor. Intermittent iilling anddrainin of a digester may be obviated by my process y nd I have provided1li-means whereby the pulp is continuously discharged from thedigestionA apparatus to improved washing and degassing apparatus.Economies in operation are eiiected by the practice l of my invention.

Generally speaking,my invention comprises a treatment of brous materialin which this material is subjected first to a water pretreatment andthen to the action of cooking liquor at elev vated temperatures andunder hydrostatic pressure, procured, for example, by the use of novelapparatus hereinafter fully described. The i'lbrous material may passcontinuously throughl this apparatus, wherein the pulp is liberated, andthe cooking liquor may then be continuously drained off and the pulpwashed while at the same time gases are liberated and vented back to arecovery system and the pulp is diluted with water or other suitablewashing liquid. The re moval of digestion liquor from the pulp is veryeffectively accomplished in my process, lresulting in an improved pulpproduct. The invention is applicable to both acid and alkaline pulpingprocesses.

My improved process and apparatus are adapted 4 for use in conjunctionwith a pretreatment of the iibrous material as described and claimed inmy co-pendingapplication, Ser. No. '753,893

nl ed November 20, 1934.

Further lbeneiicial features of my invention will in part be set forthand in part be apparent as a description is given of the accompanyingdrawing,which illustrates diagrammatically apparatus suitable for thepractice of my invention.

In this drawing, l is a pretreatment tank, pro- 5 vided with nozzles 2,through which steam may be admitted, and aline 3 with valve 4 for1 the Yadmission of water or other suitable solvent liquid. This tank may bedrained through valve 5, the contents being emptied into the casing 1,

55 which encloses a worm conveyor 6, driven by a motor 8. A steamadmission line 9 with valved branch entrances I0 is provided to admitsteam or hot liquid to the casing 1. A pump Il is provided at the end oithe worm conveyor, to pass the material up the leg or conduit l2, into'which conduit steam may be admitted through the line I3 with its valveI4.

vThe leg I2'is a vertical conduit, connected to or integral with afurther conduit l5, which contains a strainer I6. Beneath the straineris a collecting apparatus I1 and a drainage line 2i, through which thedrained water may pass. In conjunction with this collecting apparatus I1I provide a gas vent 22, with valve 23. This gas vent 22 and thedrainage line 2l are preferably both provided with seal legs or traps,`such as are show'n and described in my aforesaid co-pendingapplication, Ser. No. 753,893, now U. S. Patent No. 2,038,925, such seallegs being provided to maintain 'uid pressure on the material as itpasses through this part of the system. A storage tank for the liquiddrained through the line 2l, connecting with the pretreatment tank l,may be provided as shown inmy said co-pending application. 4

Drop leg 23a is a conduit from the strainer I6 to another worm conveyor24, encased in a casing 25, and driven by motor 26. Pipe line 21 withlavalve 28 is an admission line for either hot or cold cooking liquor froma liquor storage tank or hot acid accumulator -(not shown). 29 is asteam admission line, controlled by the va1ve'30.

' Pump 3| is Aconnected between the casing 25 and a verticalv leg 32,4which is enclosed in a steam jacket 33. Connected with the steam jacketis the steamadmission line 34 with valve 36 and also a condensateremoval line 36 with valve 31.

I also provide a steam admission line 38 with valve 39 connecteddirectly with the interior of the vertical leg 32.

Connected with the leg 32, or integral therewith, is a further conduit40, which contains a strainer 4l above a second collector 42. Thecollector 42 terminates at its bottom'in .a drain pipe 43, which isprovided with a. seal leg or trap 4'44, similar to the seal leg whichmay be pro- -vided in connection with pipe 2|, to maintain the pressure;This drain may lead to the sewer,- or to a tank for further treatment ofthe liquor.

A top relief line 45 with a control valve 46 passes from the conduit 40to means for recovering the relief gases and liquids. These recoverymeans may conveniently comprise an eductor, drop les and accumulator, asshown in connection with a digester in my aforesaid co-pendingapplication, Ser. No. 753,893. i,

A conduit or drop leg 5| connects the conduit 40 with a worm conveyor52, which is contained in the bottom of a wash tank 53. The casing 6I)of this worm conveyor is open at 'the top to communicate with theinterior of the tank 53, into which the worm discharges the pulp. ThisWash tank 53 has a hot water admission line 54, with its valve 55. Tank53 is also provided with steam admission nozzles -51, and a gas andvapor outlet line 58, which may lead to the l acid recovery or make-upsystem.

Communicating with the worm conveyor 52 -is a further vertical wormconveyor 6|, enclosed in a vertical casing 62, at the top of which is adischarge 63, which is provided with a water supply connectionv 64having valve 65. This discharge 63 is directed to a washer 66, which maybe any of a standard type, usually provided with a further water supplyconnection 68 having a valve 61. The washer 66 at its bottom isconnected by a valve 69 and conduit 10, with a debering machine 1|,which may be of usual construction. 'I'he deiibering machine is alsoprovided With outlet 12, containing valve 13.

In operation, fibrous material is placed in pretreatment tank I, where,in the presence of hot water and steam, admitted respectively by line 3and nozzles 2, it is cooked at an elevated temperature. 'I'he materialso treated may be drained from the pretreatment tank I through the valve5 into the worm conveyor Ii, where, during its passage, it is mixed withsteam supplied by the line 9, and is then pumped by the pump II into thevertical legl I2, andacross the strainer I6, where the water is removedand passes oil? through the drain pipe 2|. Gases pass through the gasvent 22. 'Ihis pretreatment to this point is the same as that describedand claimed in my aforesaid copending` application. 'Ihe pretreatmentmay be continuous by addition of one or more pretreatment tanks asrequired.

My present invention is particularly concerned with the treatment oi'the pretreated material, from this point to the debering machine..Although this treatment may be carried on withoutv the pretreatmentreferred to, the operation will be less efficient in this case.

. The drained pulp drops thrpugh the leg 23a into the operating wormconveyor 24, wherein it is mixed with either hot or cold bisulphitecooking liquor or an'y of the alkali cooking liquors from a storage tank(not shown) or from anaccumulator in the case of the hot acid method,through the admission pipe 21, and valve 28. I prefer that, as stated inmy co-pending application above referred to, the cooking liquor be at anapproximate temperature of C. at the time of introduction, although thisis by no means essential. Steam at the same time may be admitted byopening the valve 30 in the steam inlet 29.

'I'he pump 3| is put in operation, and forces the material up the leg32, in which the material is cooked, and which may be indirectly heatedby steam admitted through the inlet 34 to the steam jacket 33. Steam mayalso be directly admitted to the leg 32 by the inlet 33, if so desiredor conditions require, but this method of heating is optional and itsuse is usually dependent upon the moisture content of the particularmaterial being treated.

The height of the leg 32 creates a hydrostatic pressure at its bottom,which varies according to the height of the leg.

After passing over the top of the leg 32, the material passes throughthe conduit 40 and the spent cooking liquor is drained oil. through thestrainer 4I, collector 42 and pipe 43, either to the sewer or to a tankfor further treatment, and gases escape through the top relief line 45to the acid recovery system, thus conserving heat units.

The cooked pulp then drops through the leg 5I to the worm conveyor 52,which passes the pulp into the tank 53, where the pulp absorbs the waterand steam supplied thereto, and wherefrom gases and vapors are allowedto escape back to the acid recovery or to the make-up system through ythe connection 53. After absorbing water in the tank 53, the pulp iselevated by the worm conveyor 6I, mixed with further hot water from thepipe 64, and nallydischarged into the washer 66, where it is subjectedto the usual washing and then is passed into the deiibering machine 1I..

The time required for the passage of the material through this apparatuswill vary according to mill conditions and the character of the rawmaterial, but in general, in making a socalled semi-chemical' pulp,normally about three or four hours time is required from'the time thepulp enters the line I5 after the pretreatment, until it is dischargedinto the worm constatic pressure necessary to secure the properftreatment.

The treatment secured in the tank 53 is, in the acid pulping process,mainly one of acid dilution, the pulp absorbing water and steam, whichare present in the tank 53. As the pulp passes up the conveyor 6I, acertain amount of disintegration of the fibres takes place. The work ofthis conveyor may be done by a. good socalled trash pump, althoughtheworm is considered more eiilcient. accomplished in the tank 66, andfurther removes acids from the material before the pulp passes to thedeiibering machine.

Having thus described my invention, I claim:

l. In apparatus for cooking fibrous material in the presence ofdigestion liquor, means to separate said liquor from such materia/l, anoutlet for said separated liquor including a trap to maintain pressureon said material while removing said liquor, and a gas relief line and acontrol valve in conjunction with said separating-means.

2. In apparatus of the character described, a pretreatment tank, avertical conduit and means for forcing brous material from saidpretreatment tank through said conduit, a strainer communicating withsaid conduit, means for-removing liquor separated by said strainer and atrap in conjunction with said removing means, a second vertical conduitcommunicating with said rst conduit, and means to force iibrous materialtherethrough,y means to inject digestion liquor into said secondconduit, a second strainer connecting with said second conduit, meansfor removing digestion liquor separated by said strainer and a secondtrap in conjunction with said The iinal washing is then removing means,and means communicatingl 3. In a. process of the character described,treating brous material with heated Water, forcing the fibrous materialso treated through a vertical conduit under decreasing hydrostaticpressure, straining Water from said material while maintaining the sameunder pressure, addthe same through a second conduit under decreasinghydrostatic pressure, straining digestion liquor from said material,diluting said material with Water and steam and Washing the same.

THOMAS L. DUNBAR.

ing digestion liquor to said material and forcing

